This invention relates to the use of alkoxylated hydroxycarboxylic acid esters as solubilizers for perfume oils in water. These solubilizers may be used, for example, in cleaning compositions.
Besides the actual cleaning ingredients, increasingly more cleaning compositions both for institutional and for domestic use also contain perfume oils to give the products a pleasant fragrance which is intended to last for as long as possible in use. The cleaning compositions in question include, in particular, products for cleaning toilets, such as for example toilet blocks or toilet gels. It has been found that the use of large amounts of perfume oils leads to problems because they do not always dissolve sufficiently on contact with water.
Accordingly, there is a need for such perfume oils—which are generally insoluble in water—to be dissolved or dispersed in water with the aid of suitable auxiliaries known as solubilizers. According to WO 94/10970 A1, monoalkyl citrates whose alkyl groups must contain 7 to 10 carbon atoms are suitable for this purpose. These monoalkyl citrates are suitable for solubilizing perfume oils in so-called personal care and household products. However, there is a constant demand for other suitable and improved solubilizers. In particular, the solubilizers are expected to perform an additional function. It has been found that certain hydroxycarboxylic acid ester derivatives can satisfy this requirement.
The present invention relates to the use of esters of hydroxycarboxylic acids with alkoxylated fatty alcohols as solubilizers for perfume oils in water.
Solubilizers are substances which, through their presence, make other compounds, which are largely insoluble in a certain solvent (in the present case water), soluble or emulsifiable in that solvent.
Alkoxylated esters of hydroxycarboxylic acids are already known and are described, for example, in EP-A2-0 199 131. This document discloses low-ethoxylated citric acid alkyl esters as water-soluble surfactants, more particularly for use in cosmetic formulations. It does not state that the ethoxylated citric acid esters could be suitable for solubilizing perfume oils in water. The production of the esters of hydroxycarboxylic acids with alkoxylated fatty alcohols used in accordance with the invention is described, for example, in WO 2004/056741-A1. To this end, ethoxylated fatty alcohols are introduced with citric acid into a stirred reactor with a water separator and then heated to temperatures of up to 160° C. On completion of the reaction, the mixture is cooled and the ester is obtained by distillation.